Telescopic shaft for steering of vehicle, and telescopic shaft for steering of vehicle with cardan shaft joint

ABSTRACT

A telescopic shaft for steering of a vehicle is assembled in a steering shaft and includes a male shaft and a female shaft that are so fitted as not to be rotatable but to be slidable. Rolling members are fitted through an elastic body for pre-load between at least a pair of axially-extending grooves formed in an outer peripheral surface of the male shaft and in an inner peripheral surface of the female shaft. A slide member is fitted in between at least another pair of axially-extending grooves formed in the outer peripheral surface of the male shaft and in the inner peripheral surface of the female shaft. When a steering toque is equal to or smaller than a predetermined level, the elastic body for the pre-load exhibits a low rigidity characteristic as the elastic body performs pre-load action. When the steering torque is equal to or larger than the predetermined level, the slide member exhibits a high rigidity characteristic as the slide member engages with the pair of axially extending grooves.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 10/504,815 filedAug. 17, 2004, now U.S. Pat. No. 7,322,607 which is a 371 ofPCT/JP03/07323 filed Jun. 10, 2003.

TECHNICAL FIELD

The present invention relates to a telescopic shaft for steering of avehicle and a telescopic shaft for steering of a vehicle with a Cardanshaft joint.

BACKGROUND ARTS

In a steering apparatus for a vehicle, an intermediate shaft isprovided, for instance, between a Cardan shaft joint provided on theside of a steering shaft and a Cardan shaft joint provided on the sideof a steering gear.

The intermediate shaft is constructed of a male shaft and a female shaftthat are so spline-fitted, etc. as not to be rotatable but to beslidable on each other. The intermediate shaft is structured to becapable of transferring a steering torque in a high rigidity state whilepreventing a backlash in order to surely transfer the steering torquegiven from a driver to the steering gear, absorbing an axis-directionaldisplacement caused when the vehicle travels, and sliding(expandable/retractable) in the axial direction with a comparatively lowand stable slide load so that the intermediate shaft can be expanded andretracted when disassembled and assembled.

The intermediate shaft has, for cutting uncomfortable “noises” and“vibrations” transferred to an interior of a car room from travelingwheels and from an engine room, a buffer mechanism provided between theintermediate shaft and a yoke of the Cardan shaft joint as disclosed in,e.g., German Patent Laid-Open Publication DE19905350A1.

In this buffer mechanism, a buffer member constructed by charging aspace between an inner ring and an outer ring with a rubber, is providedbetween the intermediate shaft and the yoke of the Cardan shaft joint.When the steering torque is equal to or smaller than a predeterminedlevel, the buffer member can buffer and reduce the uncomfortable noisesand vibrations transferred from the engine room.

Note that the yoke is formed with a cut portion, while the intermediateshaft is provided with an engaging member (a protruded cam). Owing tothis configuration, when the steering torque is equal to or smaller thanthe predetermined level, the engaging member does not engage with thecut portion, and when the steering torque rises to become equal to orlarger than the predetermined level, the engaging member engages the cutportion, thus enabling the steering torque to be transferred. A feelingof sharp steering can be therefore acquired.

As described above, the intermediate shaft with the Cardan shaft jointhas the buffer function in addition to the steering torque transferfunction and the telescopic function.

It is, however, required that the buffer mechanism be provided on theside of the yoke of the Cardan shaft joint, and hence an effectiveutility space is reduced proportionally to a space for the buffermechanism. This is a comparatively narrow portion, and nevertheless ascheme of effectively utilizing the space can not be attained. Further,this is a hindrance to decrease both the number of parts andmanufacturing costs.

Moreover, a performance of absorbing the axis-directional displacementcaused when the car travels and preventing the displacement andvibrations from being transferred onto a steering wheel, is required ofthe telescopic shaft of the steering mechanism of the car. Furthermore,the telescopic shaft is required to have a function by which a drivershifts and thus adjusts a position of the steering wheel in the axialdirection in order to obtain an optimum position to driving the car.

In each of these cases, the telescopic shaft is required to reduce thebacklash noises, an unpleasant feeling about the backlash on thesteering wheel and a slide resistance during a slide operation in theaxial direction.

Such being the case, the male shaft of the telescopic shaft has hithertobeen coated with a film of nylon, and the slide portion has beengreased, thereby absorbing or relieving metal noises, metal buttingnoises, etc. and reducing the slide resistance and the backlash causedin the rotating direction.

It might, however, happen that the film of nylon is increasingly abradedwith an elapse of its use, with the result that the backlash in therotating direction augments. Further, under a condition of being exposedto a high temperature within an engine room, the film of nylon changesin its volume and remarkably increases in slide resistance, and theabrasion thereof is conspicuously accelerated, resulting in an increasein the backlash in the rotating direction.

Under such circumstances, German Patent DE3730393C2 discloses thattorque transfer members (spherical members) rolling when two shafts makerelative movements in the axial direction, are fitted in between pluralpairs of axially-extending grooves formed respectively in an outerperipheral surface of a male shaft and in an inner peripheral surface ofa female shaft.

Further, according to German Patent DE3730393C2, a pre-load elastic body(leaf spring) for giving pre-load to the male shaft and the female shaftthrough a torque transfer member (spherical member), is provided betweenan inward or outward portion of the torque transfer member (sphericalmember) in a radial direction and each pair of axially-extendinggrooves.

With this configuration, when the torque is not transferred (whensliding), the leaf spring gives the pre-load to the torque transfermember (spherical member) against the female shaft to an extent largeenough not to cause the backlash, thereby making it possible to preventthe backlash between the male shaft and the female shaft and enablingthe male shaft and the female shaft to slide in the axial direction witha stable slide load without any backlash.

Moreover, when the torque is transferred, the leaf spring is capable ofrestricting the torque transfer member (spherical member) in aperipheral direction, and therefore the male shaft and the female shaftcan transfer the torque in a high rigidity state while preventing thebacklash in the rotating direction thereof.

Besides, according to structures disclosed in FIGS. 1 through 5 inGerman Patent DE3730393C2, one leaf spring for giving the pre-load to aset of torque transfer members (spherical members) is connected in theperipheral direction to another leaf spring for giving the pre-load toanother set of torque transfer members (spherical members) adjacentthereto in the peripheral direction through a circular-arc connectingportion (web) extending in the peripheral direction.

The connecting portion (web) serves to generate the pre-load in the twoleaf springs by applying tension or compression to the two leaf springseach other.

Note that according to structures disclosed in FIGS. 6 and 7 in GermanPatent DE3730393C2, the two leaf springs are not connected through theconnecting member (web), however, a separate elastic body is interposedbetween the leaf spring and the axially-extending groove, therebygenerating the pre-load in the radial direction.

In the structure disclosed in the above Patent Document, however,firstly, the pre-load is generated between the male shaft, the sphericalmember and the female shaft, and hence a curvature of the leaf springand a curvature of the axially-extending groove has been changed so thatthe leaf spring may be disposed. The leaf spring is therefore unable totake a large quantity of flexure thereof. Note that a scatter in workingaccuracy, if any, is not allowable with the quantity of flexure to thatextent.

Secondly, when the torque is inputted, the male shaft, the leaf spring,the spherical members and the female shaft get narrow down each otherand thus transfer the torque, and therefore an extremely high surfacepressure occurs at a contact point between the spherical member and theleaf spring. Namely, when the torque is transferred, a high stressoccurs on the leaf spring, with the result that a “fatigue” of the leafspring is induced by a permanent deformation, pre-load performancebecomes hard to maintain over a long period of time, and this might be ahindrance to gain a longer life-time of the steering shaft.

Thirdly, when the torque is transferred, the leaf spring slides sidewaysin the peripheral direction from the axially-extending groove, whereby adecline of the transfer torque is induced, a degree of hysteresis cannot be managed, and the hysteresis might excessively occur.

Fourthly, when a torque load is not applied, the contact points betweenthe male shaft, the spherical member, the leaf spring and the femaleshaft do not exist on the same line, and hence contact angles change asthe torque load is applied. As a result, neither a linear torsionalcharacteristic necessary for the steering shaft nor the properhysteresis might be obtained.

It is a first object of the present invention, which was devised underthe circumstances described above, to provide a telescopic shaft forsteering of a vehicle and a telescopic shaft for steering of a vehiclewith a Cardan shaft joint that are capable of sliding with a stableslide load while surely preventing a backlash, transferring a torque ina high rigidity state and, besides, having two- or three-stagedtorsional rigidity characteristics while scheming to effectively utilizea space and to reduce the number of parts.

DISCLOSURE OF THE INVENTION

To accomplish the first object, a telescopic shaft for steering of avehicle according to a first invention is assembled in a steering shaftand including a male shaft and a female shaft that are so fitted as notto be rotatable but to be slidable, and is characterized in that:rolling members are fitted through an elastic body for pre-load betweenat least a pair of axially-extending grooves formed in an outerperipheral surface of the male shaft and in an inner peripheral surfaceof the female shaft; a slide member is fitted in between at leastanother pair of axially-extending grooves formed in the outer peripheralsurface of the male shaft and in the inner peripheral surface of thefemale shaft; and when a steering toque is equal to or smaller than apredetermined level, the elastic body for the pre-load exhibits a lowrigidity characteristic as the elastic body performs pre-load action,when the steering torque is equal to or larger than the predeterminedlevel, the slide member exhibits a high rigidity characteristic as theslide member engages with the pair of axially extending grooves, andtwo-staged torsional rigidity characteristics of the low rigiditycharacteristic and the high rigidity characteristic, are therebyprovided.

Thus, according to the first invention, when torque is transferred, twotypes of roller members and slide member are employed, and the elasticbody gives the pre-load to the rolling members against the female shaftto an extent large enough not to cause the backlash, whereby the maleshaft and the female shaft can slide with the stable slide load in theaxial direction while surely preventing the backlash between the maleshaft and the female shaft.

When the torque is transferred, the slide member engages with the pairof axially-extending grooves in the peripheral direction and can thus berestricted, and further the rolling members can be restricted in theperipheral direction by the elastic body. It is therefore possible totransfer the torque in a high rigidity state by certainly preventing thebacklash in the rotating direction between the male shaft and the femaleshaft.

Moreover, when the steering toque is equal to or smaller than thepredetermined level, the elastic body for the pre-load exhibits the lowrigidity characteristic as the elastic body performs pre-load action. Onthe other hand, when the steering torque is equal to or larger than thepredetermined level, the slide member exhibits the high rigiditycharacteristic as the slide member engages with the pair of axiallyextending grooves in the peripheral direction.

Namely, when the steering torque is equal to or smaller than thepredetermined level, the elastic body buffers and thus reducesuncomfortable noises and vibrations transferred from an engine room bythe pre-load action thereof. While on the other hand, when the steeringtorque rises to become equal to or larger than the predetermined level,the slide member engages with the pair of axially-extending grooves inthe peripheral direction, and can thus transfer the steering torque,whereby a feeling of sharp steering can be acquired.

Accordingly, the torque transfer/slide mechanism serves also as a buffermechanism, and hence it is possible to provide the telescopic shaftexhibiting the two-staged torsional rigidity characteristics in a waythat effectively makes the use of a space and reduces both of the numberof parts and manufacturing costs.

A telescopic shaft for steering of a vehicle with a Cardan shaft jointaccording to a second invention is assembled in a steering shaft,including a male shaft and a female shaft that are so fitted as not tobe rotatable but to be slidable, and receiving a connection of a yoke ofa Cardan shaft joint, and is characterized in that: rolling members arefitted through an elastic body for pre-load between at least a pair ofaxially-extending grooves formed in an outer peripheral surface of themale shaft and in an inner peripheral surface of the female shaft; aslide member is fitted in between at least another pair ofaxially-extending grooves formed in the outer peripheral surface of themale shaft and in the inner peripheral surface of the female shaft; abuffer member is interposed between the yoke and any one of the maleshaft and the female shaft; the yoke is formed with an engaged portion,and any one of the male shaft and the female shaft is provided with anengaging member capable of engaging with and disengaging from theengaged portion; and when a steering toque is equal to or smaller than apredetermined level, the engaging member does not engage with theengaged portion while the buffer member exhibits a low rigiditycharacteristic as the buffer member performs buffer action, when thesteering torque falls within a predetermined intermediate range, theelastic body for the pre-load exhibits an intermediate rigiditycharacteristic as the elastic body performs pre-load action, when thesteering torque is equal to or larger than the predetermined level, theengaging member engages with the engaged portion while the slide memberexhibits a high rigidity characteristic as the slide member engages withthe pair of axially-extending grooves in a peripheral direction, andthree-staged torsional rigidity characteristics of the low rigiditycharacteristic, the intermediate rigidity characteristic and the highrigidity characteristic, are thereby provided.

Thus, according to the second invention, when the steering torque isequal to or smaller than the predetermined level, the engaging memberdoes not engage with the engaged portion, and the buffer member exhibitsthe low rigidity characteristic as it performs the buffer action. Whenthe steering torque is within the predetermined intermediate range, theelastic body for the pre-load exhibits the intermediate rigiditycharacteristic as it performs the pre-load action. On the other hand,when the steering torque is equal to or larger than the predeterminedlevel, the engaging member engages with the engaged portion, and theslide member engages with the pair of axially-extending grooves in theperipheral direction and exhibits the high rigidity characteristic.

Namely, when the steering torque is equal to or smaller than thepredetermined level, the engaging member does not engage with theengaged portion, and the buffer member can buffer and thus reduce theuncomfortable noises and vibrations transferred from the engine room.When the steering torque is within the predetermined intermediate range,the elastic body for the pre-load raises the torsional rigidity stepwiseby the pre-load action thereof. On the other hand, when the steeringtorque rises to become equal to or larger than the predetermined level,the engaging member engages with the engaged portion, and the slidemember engages with the pair of axially-extending grooves in theperipheral direction, thus transferring the steering torque. The feelingof sharp steering can be therefore acquired.

Accordingly, if the telescopic shaft serves also as a torquetransfer/slide/buffer mechanism, the buffer mechanism is providedseparately on the yoke-side, the telescopic shaft having thethree-staged torsional rigidity characteristics can be provided.

It is an object of a third invention of the present application toprovide a telescopic shaft for steering of a vehicle that is capable ofactualizing a stable slide load, surely preventing the backlash in therotating direction, transferring the torque in the high rigidity state,besides setting a quantity of flexure of the leaf spring comparativelylarge, improving durability of pre-load performance, preventinghysteresis from becoming excessive, and acquiring a linear torsionalcharacteristic necessary for the steering shaft.

A telescopic shaft for steering of a vehicle according to the thirdinvention is assembled in a steering shaft and including a male shaftand a female shaft that are so fitted as not to be rotatable but to beslidable, and is characterized in that: a first torque transfer memberis interposed through an elastic body in at least one line ofaxially-extending groove formed in each of an outer peripheral surfaceof the male shaft and an inner peripheral surface of the female shaft; asecond torque transfer member is interposed between at least anotherline of axially-extending groove formed in each of the outer peripheralsurface of the male shaft and the inner peripheral surface of the femaleshaft; and the elastic body includes a transfer member sided contactportion making contact with the first torque transfer member, a groovesurface sided contact portion spaced at a predetermined intervalsubstantially in a peripheral direction from the transfer member sidedcontact portion, and making contact with a groove surface of theaxially-extending groove of the male shaft or the female shaft, and abiasing portion elastically biasing the transfer member sided contactportion and the groove surface sided contact portion in such a directionas to get separated from each other.

Thus, according to the third invention, the elastic body includes thetransfer member sided contact portion making contact with the firsttorque transfer member, the groove surface sided contact portion spacedat the predetermined interval substantially in the peripheral directionfrom the transfer member sided contact portion, and making contact withthe groove surface of the axially-extending groove of the male shaft orthe female shaft, and the biasing portion elastically biasing thetransfer member sided contact portion and the groove surface sidedcontact portion in such a direction as to get separated from each other.Accordingly, the elastic body, with its transfer member sided contactportion capable of getting sufficiently flexural through the biasingportion, is therefore capable of ensuring an ample quantity of flexurethereof.

Further, because of including the second torque transfer member inaddition to the first torque transfer members, when the torque istransferred, the second torque transfer member makes contact with theaxially-extending grooves of the male shaft and of the female shaftearlier than the excessive load (stress) is applied on the elastic body,and are capable of mainly transferring the torque, and consequently theexcessive load (stress) is applied on neither the first torque transfermembers nor the elastic body.

Moreover, the elastic body can ensure the sufficient quantity offlexure, and the excessive load (stress) is applied on neither the firsttorque members nor the elastic body. Therefore, when the torque istransferred, the stress generated at the contact portion between thefirst torque member and the elastic body can be relieved, whereby noneof the high stress occurs and the pre-load performance can be maintainedover a long period of time by preventing a “fatigue” due to thepermanent deformation.

Still further, in the elastic body, the transfer member sided contactportions thereof are in contact with the first torque transfer member,and the groove surface sided contact portions thereof are in contactwith the groove surfaces of the axially-extending groove. Therefore, theelastic body is in the state of fitting into the axially-extendinggroove. Accordingly, when the torque is transferred, the whole of theelastic body is hard to slide sideways in the peripheral direction fromthe axially-extending groove. Hence, a decrease in the transfer torqueis not induced, and the hysteresis can be prevented from becomingexcessive.

Furthermore, contact points between the male shaft, the sphericalmember, the elastic body and the female shaft stay on the same lineirrespective of the state of the torque load, and therefore the contactangle does not change. This makes it possible to acquire the lineartorsional characteristic necessary for the steering shaft and also alinear steering characteristic giving the feeling of the high rigidity.

Note that manufacturing errors of the male shaft, the female shaft andthe elastic body can be absorbed by the elastic deformation of theelastic body, so that machining of the groove is not required, and thecosts can be reduced.

In the telescopic shaft for the steering of the vehicle according to thethird invention, preferably the first torque transfer member may be arolling member that rolls when the two shafts make relative movements inthe axial direction, and the second torque transfer member may be aslide member that slides when the two shafts make the relative movementsin the axial direction. Thus, the first torque transfer member is therolling member that rolls when the two shafts make relative movements inthe axial direction, and the second torque transfer member may be aslide member that slides when the two shafts make the relative movementsin the axial direction. Hence, when the torque is transferred, thesecond torque transfer member as the slide member makes contact with theaxially-extending groove of the male shaft and of the female shaftearlier than the excessive load (stress) is applied on the elastic body,and is capable of mainly transferring the torque, and consequently theexcessive load (stress) is applied on neither the first torque transfermember as the rolling member nor the elastic body. Therefore, whensetting and when the torque is transferred, the stress generated at thecontact portion between the rolling member and the elastic body can berelieved, whereby the pre-load performance can be maintained over thelong period of time by preventing the “fatigue” due to the permanentdeformation.

In the telescopic shaft for the steering of the vehicle according to thethird invention, preferably, the biasing portion of the elastic body maytake a bent shape bent between the transfer member sided contact portionand the groove surface sided contact portion. Thus, the biasing portionof the elastic body may take a bent shape bent between the transfermember sided contact portion and the groove surface sided contactportion. The biasing portion in the bent shape can elastically bias thetransfer member sided contact portion and the groove surface sidedcontact portion so as to get separated from each other.

In the telescopic shaft for the steering of the vehicle according to thethird invention, preferably, the axially-extending groove of the maleshaft or the female shaft may have a flat side surface making contactwith the groove surface sided contact portion of the elastic body, and abottom surface contiguous to the flat side surface, the elastic body mayhave a bottom portion facing the bottom surface of the axially-extendinggroove, and the bottom portion of the elastic body may be set in acontact state with the bottom surface of the axially-extending groove,or an interval between the bottom surface of the axially-extendinggroove and the bottom portion of the elastic body may be set to apredetermined interval.

Hence, the bottom portion of the elastic body is made contact with thebottom surface of the axially-extending groove as the necessity mayarise, thereby making it possible to control the hysteresis and toobtain the hysteresis as desired.

Namely, it is required that the hysteresis be changed in many ways inmatching with the steering performance of each vehicle. To be specific,in a case where the bottom portion of the elastic body is set in thecontact-state with the bottom surface of the axially-extending groove, afriction occurs when the axially-extending groove and the elastic bodymake relative movements, and the hysteresis can be set comparativelylarge. On the other hand, an interval between the bottom surface of theaxially-extending groove and the bottom portion of the elastic body isset to a predetermined interval, in which case none of the frictionoccurs when the axially-extending groove and the elastic body make therelative movements, and the hysteresis can be set comparatively small.

In the telescopic shaft for the steering of the vehicle according to thethird invention, preferably the biasing portion of the elastic body maybe a separate portion from the transfer member sided contact portion andfrom the groove surface sided contact portion, and may be formed of adifferent material. Thus, the biasing portion of the elastic body is aseparate portion from the transfer member sided contact portion and fromthe groove surface sided contact portion, and is formed of the differentmaterial. Therefore, when the torque is transferred, the stressgenerated at the biasing portion can be made comparatively small.

In the telescopic shaft for the steering of the vehicle according to afourth invention, preferably, the elastic body includes, in addition tothe transfer member sided contact portion, the groove surface sidedcontact portion and the biasing portion, a second biasing portionprovided formed of a different material as a separate portion. Thus, theelastic body may include, in addition to the transfer member sidedcontact portion, the groove surface sided contact portion and thebiasing portion, the second biasing portion provided formed of thedifferent material as the separate portion, whereby the steeringcharacteristic giving the feeling of desired high rigidity can beacquired owing to the two biasing portions.

In the telescopic shaft for the steering of the vehicle according to thefourth invention, preferably, the elastic body is constructed of a leafspring. Thus, the elastic body is constructed of the leaf spring,whereby the steering characteristic giving the feeling of the desiredhigh rigidity can be obtained while restraining the manufacturing costs.

In the telescopic shaft for the steering of the vehicle according to thefourth invention, preferably, the biasing portion provided as theseparate portion and formed of the different material and the secondbiasing portion provided as the separate portion and formed of thedifferent material, are made of a rubber or a synthetic resin. Thus, thebiasing portion provided as the separate portion and formed of thedifferent material and the second biasing portion provided as theseparate portion and formed of the different material, are made of therubber or the synthetic resin, whereby the stress generated at thebiasing portion when the torque is transferred can be made comparativelysmall, and the steering characteristic giving the feeling of desiredhigh rigidity can be acquired.

In the telescopic shaft for the steering of the vehicle according to thefourth invention, preferably, a lubricating agent is applied between theaxially-extending groove of the male shaft, the axially-extending grooveof the female shaft, the elastic body and the first torque transfermember. Thus, the lubricating agent is applied between theaxially-extending groove of the male shaft, the axially-extending grooveof the female shaft, the elastic body and the first torque transfermember, whereby when the torque is not transferred (when sliding), themale shaft and the female shaft can slide in the axial direction withthe stable slide load without any backlash.

From what has been discussed so far, according to the fourth invention,the stress generated on the elastic body is relieved, whereby thepre-load performance required over the long period of time can bemaintained by preventing the “fatigue” of the elastic body. Further,there is no necessity of setting the dimensional accuracy strict, andthe reduction in the costs can be actualized. Moreover, the steeringperformance required can be easily obtained because of being structuredso that the friction between the elastic body and the axially-extendinggroove can be controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a steering mechanism unit of a car,to which a telescopic shaft for steering of a vehicle according to anembodiment of the present invention is applied;

FIG. 2 is a vertical sectional view of the telescopic shaft for thesteering of the vehicle with a Cardan shaft joint according to a firstembodiment of the present invention;

FIG. 3 is an exploded perspective view of the telescopic shaft for thesteering of the vehicle shown in FIG. 2;

FIG. 4 is a cross-sectional view taken along the line III-III in FIG. 2;

FIG. 5 is a graph (a part 1) showing a relationship between a steeringtorque and a rotational angle;

FIG. 6 is a graph (a part 2) showing the relationship between thesteering torque and the rotational angle;

FIG. 7 is a graph (a part 3) showing the relationship between thesteering torque and the rotational angle;

FIG. 8 is a cross-sectional view similar to FIG. 4, showing a firstmodified example of the first embodiment of the present invention;

FIG. 9 is a cross-sectional view similar to FIG. 4, showing a secondmodified example of the first embodiment of the present invention;

FIG. 10 is a cross-sectional view similar to FIG. 4, showing a thirdmodified example of the first embodiment of the present invention;

FIG. 11 is a cross-sectional view similar to FIG. 4, showing a fourthmodified example of the first embodiment of the present invention;

FIG. 12A is a vertical sectional view of the telescopic shaft for thesteering of the vehicle with a Cardan shaft joint according to a secondembodiment of the present invention; FIG. 12B is a cross-sectional viewtaken along the line b-b in FIG. 12A;

FIG. 13A is a side view including a partial cut-off section of asub-assembly of the telescopic shaft for the steering of the vehiclewith the Cardan shaft joint shown in FIGS. 12A and 12B; FIG. 13B is aside view including a partial cut-off section of a female shaft; FIG.13C is a front view of the female shaft as viewed from the left side;

FIG. 14 is a graph showing a relationship between the steering torqueand the rotational angle in the second embodiment.

FIG. 15A is a vertical sectional view of the telescopic shaft for thesteering of the vehicle with the Cardan shaft joint according to amodified example of the second embodiment of the present invention; FIG.15B is a cross-sectional view taken along the line b-b in FIG. 15A;

FIG. 16A is a vertical sectional view of the telescopic shaft for thesteering of the vehicle with the Cardan shaft joint according to a thirdembodiment of the present invention; FIG. 16B is a cross-sectional viewtaken along the line b-b in FIG. 16A;

FIG. 17 is a side view including a partial cut-off section of the femaleshaft of the telescopic shaft for the steering of the vehicle with theCardan shaft joint shown in FIG. 15A;

FIG. 18A is a vertical sectional view of the telescopic shaft for thesteering of the vehicle according to a fourth embodiment of the presentinvention; FIG. 18B is a perspective view of a leaf spring as an elasticbody;

FIG. 19 is a cross-sectional view taken along the line X-X in FIG. 18A;

FIG. 20 is an enlarged partial sectional view of the telescopic shaftfor the steering of the vehicle in the fourth embodiment of the presentinvention, showing a state when the torque is not transferred;

FIG. 21 is an enlarged partial sectional view of the telescopic shaftfor the steering of the vehicle in the fourth embodiment of the presentinvention, showing a state when the torque is transferred;

FIGS. 22A, 22B and 22C are schematic views showing flexural states ofleaf springs employed in the fourth embodiment of the present invention;

FIG. 23 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a fifth embodiment of the presentinvention;

FIG. 24 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a sixth embodiment of the presentinvention;

FIG. 25 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a seventh embodiment of the presentinvention;

FIG. 26 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in an eighth embodiment of the presentinvention;

FIG. 27 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a ninth embodiment of the presentinvention;

FIG. 28 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a tenth embodiment of the presentinvention;

FIG. 29 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in an eleventh embodiment of the presentinvention;

FIG. 30 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a twelfth embodiment of the presentinvention;

FIG. 31 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a thirteenth embodiment of the presentinvention;

FIG. 32 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a fourteenth embodiment of the presentinvention;

FIG. 33 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a fifteenth embodiment of the presentinvention;

FIG. 34 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a sixteenth embodiment of the presentinvention;

FIG. 35 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a seventeenth embodiment of the presentinvention;

FIG. 36 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in an eighteenth embodiment of the presentinvention;

FIG. 37 is an enlarged partial sectional view of a telescopic shaft forsteering of a vehicle in German Patent DE3730393C2, showing a state whenthe torque is not transferred;

FIG. 38 is an enlarged partial sectional view of the telescopic shaftfor the steering of the vehicle in German Patent DE3730393C2, showing astate when the torque is transferred; and

FIGS. 39A and 39B are schematic views each showing a flexural state ofthe leaf spring used in German Patent DE3730393C2.

EMBODIMENTS OF THE INVENTION

A telescopic shaft for steering of a vehicle according an embodiment ofthe present invention will hereinafter be described with reference tothe accompanying drawings.

(Whole Construction of Steering Shaft for Vehicle)

FIG. 1 is a side view of a steering mechanism unit of a car, to whichthe telescopic shaft for the steering of the vehicle according to theembodiment of the present invention is applied.

Referring to FIG. 1, the steering mechanism unit is constructed of: anupper steering shaft member 120 (including a steering column 103 and asteering shaft 104 a rotatably held in the steering column 103) securedto a car-body-sided member 100 through an upper bracket 101 and a lowerbracket 102; a steering wheel 105 fitted to an upper end of the steeringshaft 104; a lower steering shaft member 107 connected through auniversal joint 106 to a lower end of the steering shaft 104; a pinionshaft 109 connected through a steering shaft joint 108 to the lowersteering shaft member 107; a steering rack shaft 112 connected to thepinion shaft 109; and a steering rack support member 113 supporting thesteering rack shaft 112 and fixed to a different frame 110 of the carbody through an elastic body 111.

Herein, the upper steering shaft member 120 and the lower steering shaftmember 107 involve the use of the telescopic shaft for the steering ofthe vehicle (which will hereinafter be simply termed “the telescopicshaft”) according to the embodiment of the present invention. The lowersteering shaft member 107 is assembled by fitting a male shaft and afemale shaft to each other. This type of lower steering shaft member 107is, however, required to have performance of absorbing displacement inthe axial direction that occurs when the car travels, and of preventingthe displacement and vibrations from being transferred onto the steeringwheel 105. This performance is required for such a configuration thatthe car body takes a sub-frame structure, wherein the member 100 forfixing an upper part of the steering mechanism is separated from theframe 110 to which the steering rack support member 113 is fixed, andthe steering rack support member 113 is fixed by fastening to the frame110 through the elastic body 111 such as a rubber, etc. Further, anothercase is that a worker, when fastening the steering shaft joint 108 tothe pinion shaft 109, temporarily contracts the telescopic shaft andthereafter secures the joint 108 to the pinion shaft 109 by fastening,and hence there is an instance of requiring an telescopic function.Moreover, the upper steering shaft member 120 provided at the upper partof the steering mechanism is, though configured likewise by fitting themale shaft and the female shaft together, is required to include afunction of adjusting, on such an occasion that a driver shifts aposition of the steering wheel 105 in the axial direction in order togain an optimum position for driving the car, this position and istherefore demanded to have the telescopic function in the axialdirection. It is required in all the cases described above to reducebacklash noises at fitting portion in the telescopic shaft, to relieve auncomfortable feeling to the backlash on the steering wheel 105 and todecrease a slide resistance when slid in the axial direction.

First Embodiment

FIG. 2 is a vertical sectional view of the telescopic shaft for thesteering of the vehicle with a Cardan shaft joint according to a firstembodiment of the present invention. FIG. 3 is an exploded perspectiveview of the telescopic shaft for the steering of the vehicle shown inFIG. 2. FIG. 4 is a cross-sectional view taken along the line III-III inFIG. 2. FIG. 5 is a graph (a part 1) showing a relationship between asteering torque and a rotational angle. FIG. 6 is a graph (a part 2)showing the relationship between the steering torque and the rotationalangle. FIG. 7 is a graph (a part 3) showing the relationship between thesteering torque and the rotational angle.

As illustrated in FIG. 2, the telescopic shaft for the steering of thevehicle (which will hereinafter be termed an “telescopic shaft”) isconstructed of a male shaft 1 and a female shaft 2 that are fitted so asnot to be rotatable but to be slidable on each other.

The male shaft 1 is connected to a yoke 21 of a Cardan shaft joint 20 onthe side of the steering wheel. The female shaft 2 is connected to ayoke 23 of a Cardan shaft joint 22 on the side of a steering gear.

As shown in FIG. 3, three pairs of grooves 3, 4 each takingsubstantially a circular-arc shape and extending in the axial direction,are formed in an outer peripheral surface of the male shaft 1 in a waythat disposes these grooves equally at an interval of 120 degrees in aperipheral direction thereof. Correspondingly in an inner peripheralsurface of the female shaft 2, three pairs of grooves 5, 6 each takingsubstantially the circular-arc shape and extending in the axialdirection, are formed in a way that disposes these grooves equally atthe interval of 120 degrees in the peripheral direction thereof.

A plurality of balls 7 (spherical rolling members) are disposed setrollable in each pair of the axially-extending groove 3, takingsubstantially the circular-arc shape, of the male shaft 1 and theaxially-extending groove 5, taking substantially the circular-arc shape,of the female shaft 2 through a corrugated leaf spring 9 for pre-load.Note that stopper portions 3 a for stopping the leaf spring 9 are formedon both sides of each axially-extending groove 3 of the male shaft 1.

A needle roller 8 (a slide member) is slidably disposed between theaxially-extending groove 4, taking substantially the circular-arc shape,of the male shaft 1 and the corresponding line of axially-extendinggroove 6, taking substantially the circular-arc shape, of the femaleshaft 2.

Each leaf spring 9 works to give pre-load to the balls 7 and the needleroller 8 against the female shaft 2 to an extent large enough not tocause a backlash when the torque is not transferred, and also works torestrain the balls 7 between the female shaft 2 and the spring plate 9itself in the peripheral direction as the leaf spring 9 elasticallydeforms when the torque is transferred.

A periphery-directional groove 10 is formed in a side end portion of themale shaft 1. With this contrivance, a stopper plate 11 is fitted in theperiphery-directional groove 10, and the needle roller 8 is fixed in theaxial direction in such a form as to be sandwiched in between the sideend of the stoppers plate and internal side end surfaces of theaxially-extending grooves 3 and 4. The internal side end surfaces of theaxially-extending grooves 3, 4 may be inclined or substantiallyright-angled to the axis.

Further, as illustrated in FIG. 4, each of the leaf springs 9 islatched, at its concave portions 9 c formed at both of its side endportions, by the stopped portions 3 a provided on both sides of theaxially-extending groove 3, thereby making the whole leaf spring 9unable to move in the peripheral direction when the torque istransferred.

In the thus structured telescopic shaft, when torque is transferred, theballs 7 and the needle rollers 8 are used respectively for “rolling” and“sliding”, and each leaf spring 9 gives the pre-load to the balls 7against the female shaft 2 to the extent large enough not to cause thebacklash. It is therefore possible to surely prevent the backlashbetween the male shaft 1 and the female shaft 2, whereby the male shaft1 and the female shaft 2 can be slid in the axial direction with astable slide load but with no backlash.

When the torque is transferred, as shown in FIG. 4, the needle rollers 8interposed between the male shaft 1 and the female shaft 2 perform amain function of transferring the torque. For instance, when the torqueis inputted from the male shaft 1, as the pre-load is applied from theleaf springs 9 at an initial stage, there is no backlash, and the leafsprings 9 generates reactive forces to the torque, thus transferring thetorque. At this time, the torque is transferred on the whole in a stateof equilibrium between a torque transfer load among the male shaft 1,the leaf springs 9, the balls 7 and the female shaft 2, and a torquetransfer load among the male shaft 1, the needle rollers 8 and thefemale shaft 2.

As the torque further increases, as shown in FIG. 4, a gap in a rotatingdirection between the male shaft, the needle rollers 8 and the femaleshaft 2 has been set smaller than a gap between the male shaft 1, theleaf springs 9, the balls 7 and the female shaft 2, and hence the needlerollers 9 receive the reactive force stronger than the balls 7 receive,and mainly transfer the torque to the female shaft 2. It is thereforefeasible to surely prevent the backlash in the rotating directionbetween the male shaft 1 and the female shaft 2 and also to transfer thetorque in a high-rigidity state.

Moreover, when the steering torque is equal to or smaller than apredetermined level, each of the pre-load leaf springs 9 performs thepre-load operation to exhibit a low-rigidity characteristic, while theneedle rollers 8, when the steering torque is equal to or larger thanthe predetermined level, respectively engage with the pair ofaxially-extending grooves 4, 6 in the peripheral direction to exhibit ahigh-rigidity characteristic.

Namely, when the steering torque is equal to or smaller than thepredetermined level, the leaf springs 9 buffer and reduce theuncomfortable noises and vibrations transferred from an engine room bythe pre-load action. While on the other hand, when the steering torquerises to become equal to or larger than the predetermined level, theneedle rollers 8 respectively engage with the pair of axially-extendinggrooves 4, 6, whereby the steering torque can be transferred. Therefore,a feeling of sharp steering can be acquired.

Accordingly, the torque transfer/slide mechanism serves also as a buffermechanism, and hence it is possible to provide the telescopic shaftexhibiting the torsional rigidity characteristics at two stages in a waythat effectively makes the use of the space and reduces both of thenumber of parts and manufacturing costs.

FIG. 5 is the graph (the part 1) showing the relationship between thesteering torque and the rotational angle. In this case, since a springconstant of the leaf spring 9 is high, the rigidity in a pre-loadrigidity (low rigidity) region is high, and a torsional rigidity that isnot so different from a high rigidity region is shown. Thecharacteristic herein is, though much of the buffer function is notacquired, suited to a case where the high rigidity is required also in alow torque region.

FIG. 6 is the graph (the part 2) showing the relationship between thesteering torque and the rotational angle. This case represents a statewhere the spring constant of the leaf spring 9 is set slightly lowerthan the state in FIG. 5 (the part 1), and the characteristic herein isrequired for a case of scheming to establishing compatibility betweenthe buffer characteristic and the torsional rigidity.

FIG. 7 is the graph (the part 3) showing the relationship between thesteering torque and the rotational angle. This case represents a statewhere the spring constant of the leaf spring 9 is set slightly lowerthan the state in FIG. 6 (the part 2), and the characteristic herein isin such a case that a further buffer characteristic is demanded.

FIGS. 8 through 11 are cross-sectional views similar to FIG. 4,respectively showing first through fourth modified examples of the firstembodiment of the present invention. The first through fourth modifiedexamples are different from the first embodiment illustrated in FIGS. 2through 4 in terms of a structure and a configuration of an elasticmember including the leaf spring, and in terms of a sectional shape ofthe male shaft attached with the elastic member.

FIG. 8 shows the first modified example of the first embodiment, whereinan elastic body corresponding to the leaf spring 9 in FIGS. 2 through 4is structured as a composite body consisting of a leaf spring member 40and an elastic member 41 formed of a rubber (or a synthetic resin, etc.which is a different material from the leaf spring member 40. The rubberelastic member 41 is fixed by bonding to the leaf spring member 40, thusattaining an integral structure. The leaf spring member 40 has anaddition of the rubber elastic member 41 and therefore improves itsbuffer performance.

Crooked or bent portions 40 c, 40 a of the leaf spring member 40 arepushed by balls 7 and thereby exhibit a spring property.

Further, the rubber elastic member 41 is interposed between the crookedportions 40 a and 40 of the leaf spring member 40, whereby compositeaction with the leaf spring member enhances the buffer performance.

FIG. 9 shows the second modified example of the first embodiment,wherein the elastic body corresponding to the leaf spring 9 in FIGS. 2through 4 takes a structure in which the rubber elastic member isremoved from the elastic body shown in FIG. 8. The elastic body, even inthe case of being thus formed of a single material without the rubberelastic member 41, has a function as the elastic body.

Leaf spring members 40 a apply the pre-load to the ball 7 on one handand serve as race surfaces for the ball 7 on the other hand.

FIG. 10 shows the third modified example of the first embodiment,wherein the elastic body corresponding to the leaf spring 9 in FIG. 2through 4 is a composite body consisting of a leaf spring member 42,rubber elastic members 43 and race surface members 42 a for the ball 7.The rubber elastic members 43 are fixed by bonding to the race surfacemembers 42 a, thus attaining an integral structure. The leaf springmember 42 has an addition of the rubber elastic members 43 and cantherefore improve its buffer performance. Bent portions 42 b of the leafspring member 42 are pushed by the balls 7 through the rubber elasticmembers 43 and the race surface members 42 a, and hence composite actionthereof enhances the buffer function. The race surface member 42 is flatin shape.

FIG. 11 shows the fourth modified example of the first embodiment,wherein an elastic body 44 corresponding to the leaf spring 9 in FIGS. 2through 4 takes a shape similar to that in the third modified example,however, a race surface member 44 a in the fourth embodiment isstructured to have a radius that is larger by 5%-50% than a radius ofthe ball 7 and have a larger area in its contact portion than in thesecond modified example.

With this contrivance, a local surface pressure of the contact portioncan be restrained from rising.

The buffer performance is the same as in the second modified example.

Second Embodiment

FIG. 12A is a vertical sectional view of the telescopic shaft for thesteering of the vehicle with a Cardan shaft joint according to a secondembodiment of the present invention. FIG. 12B is a cross-sectional viewtaken along the line b-b in FIG. 12A.

FIG. 13A is a side view including a partial cut-off section of asub-assembly of the telescopic shaft for the steering of the vehiclewith the Cardan shaft joint shown in FIGS. 12A and 12B. FIG. 13B is aside view including a partial cut-off section of a female shaft. FIG.13C is a front view of the female shaft as viewed from the left side.

FIG. 14 is a graph showing a relationship between the steering torqueand the rotational angle in the second embodiment.

In the second embodiment, a buffer member 30 structured by charging aspace between an inner ring 31 and an outer ring 32 with a rubber 33, isprovided between an end portion of a female shaft 2 and a yoke 23 of aCardan shaft joint 22. When the steering torque is equal to or smallerthan a predetermined level, the buffer member 30 can buffer and thusreduce the uncomfortable noises and vibrations transferred from theengine room. Note that the buffer member 30 may also be of a rubbercoupling type.

Moreover, as shown in FIGS. 12B and 13C, the yoke 23 is formed with cuts34 (engaged portions), and cam flanges 35 (engaging members) capable ofengaging with and disengaging from the cuts 34 are provided at the endportion of the female shaft 2. Incidentally, the numeral 38 represents acap for preventing dusts from entering.

Owing to this configuration, the cam flanges 35 do not engage with thecuts 34 when the steering torque is equal to or smaller than thepredetermined level, but engage with the cuts 34 when the steeringtorque increases to become equal to or larger than the predeterminedlevel, whereby it is possible to transfer the steering torque andtherefore possible to acquire the feeling of sharp steering.

Thus, according to the second embodiment, when the steering torque isequal to or smaller than the predetermined level, the cam flanges 35 donot engage with the cuts 34, and the buffer member 30 exhibits the lowrigidity characteristic as it performs the buffer action. When thesteering torque is within a predetermined intermediate range, the leafspring 9 for the pre-load exhibits an intermediate rigiditycharacteristic as it performs the pre-load action. On the other hand,when the steering torque is equal to or larger than the predeterminedlevel, the cam flanges 35 engage with the cuts 34, and the needlerollers 8 engage with the pair of axially-extending grooves 4, 6 in theperipheral direction and exhibit the high rigidity characteristic.

Namely, when the steering torque is equal to or smaller than thepredetermined level, the cam flanges 35 do not engage with the cuts 34,and the buffer member 30 can buffer and thus reduce the uncomfortablenoises and vibrations transferred from the engine room. When thesteering torque is within the predetermined intermediate range, the leafspring 9 for the pre-load raises the torsional rigidity stepwise as itperforms the pre-load action. On the other hand, when the steeringtorque rises to become equal to or larger than the predetermined level,the cam flanges 35 engage with the cuts 34, and the needle rollers 8engage with the pair of axially-extending grooves 4, 6 in the peripheraldirection, thus transferring the steering torque. The feeling of sharpsteering can be therefore acquired.

Accordingly, if the telescopic shaft serves also as the torquetransfer/slide/buffer mechanism, the buffer mechanism is providedseparately on the yoke-side, the telescopic shaft having thethree-staged torsional rigidity characteristics can be provided.

FIG. 14 is a graph showing a relationship between the steering torqueand the rotational angle in the second embodiment. The buffer functionis exhibited in a rigidity region of the rubber 33 of the buffer member30, the torsional rigidity is increased stepwise by the leaf spring 9 ina higher torque region (an intermediate rigidity region), and the torquecan be transferred with a high rigidity in a much higher torque region(a high rigidity region).

Thus, the three-staged torsional rigidity characteristics more excellentthan the two-staged torsional rigidity characteristics, can be acquired.Hence, the torsional rigidity characteristics can be combined withoutany restrictions in accordance with characteristics demanded of thevehicle, a space and costs thereof, and both of the improvement of thefeeling of the steering and the buffer function can be set as desired.

FIG. 15A is a vertical sectional view of the telescopic shaft for thesteering of the vehicle with the Cardan shaft joint according to amodified example of the second embodiment of the present invention. FIG.15B is a cross-sectional view taken along the line b-b in FIG. 15A.

In this modified example, a buffer member 46 is disposed outwardly ofthe yoke. The buffer member 46 is constructed of an inner ring 47, anouter ring 49 and a rubber 48 with which a space between these inner andouter rings is charged. An inner peripheral surface of the inner ring 47is fixedly fitted on an outer peripheral surface of the yoke. The outerring 49 takes substantially a U-shape in section, and an inner peripheryof an inside-diametrical portion thereof is fixedly fitted on the femaleshaft 2.

According to the present modified example, a size of the rubber servingas the elastic member can be increased, and it is therefore possible toabsorb the uncomfortable noises and vibrations transferred from theengine in a much broader frequency band.

Third Embodiment

FIG. 16A is a vertical sectional view of the telescopic shaft for thesteering of the vehicle with the Cardan shaft joint according to a thirdembodiment of the present invention. FIG. 16B is a cross-sectional viewtaken along the line b-b in FIG. 16A.

FIG. 17 is a side view including a partial cut-off section of the femaleshaft of the telescopic shaft for the steering of the vehicle with theCardan shaft joint shown in FIGS. 16A and 16B.

In the third embodiment also, the buffer member 30 structured bycharging the space between the inner ring 31 and the outer ring 32 withthe rubber 33, is provided between the end portion of the female shaft 2and the yoke 23 of the Cardan shaft joint 22. When the steering torqueis equal to or smaller than the predetermined level, the buffer member30 can buffer and thus reduce the uncomfortable noises and vibrationstransferred from the engine room.

Moreover, as shown in FIGS. 16A and 17, the yoke 23 is formed with anengaged hole 36 (an engaged portion), and a stopper pin (an engagingmember) capable of engaging with and disengaging from the engaged hole36 is provided at the end portion of the female shaft 2. Incidentally,the numeral 38 designates the cap for preventing dusts from entering.

With this configuration, the stopper pin 37 does not engage with theengaged hole 36 when the steering torque is equal to or smaller than thepredetermined level, but engages with the engaged portion 36 when thesteering torque rises to become equal to or larger than thepredetermined level, whereby it is possible to transfer the steeringtorque and therefore possible to acquire the feeling of sharp steering.

Thus, according to the third embodiment, when the steering torque isequal to or smaller than the predetermined level, the stopper pin 37does not engage with the engaged hole 36, and the buffer member 30 canbuffer and thus reduce the uncomfortable noises and vibrationstransferred from the engine room. When the steering torque is within thepredetermined intermediate range, the leaf springs 9 for the pre-loadraise the torsional rigidity stepwise by the pre-load action. On theother hand, when the steering torque is equal to or larger than thepredetermined level, the stopper pin 37 engages with the engaged hole36, and the needle rollers 8 engage with the pair of axially-extendinggrooves 4, 6 in the peripheral direction, whereby the feeling of sharpsteering can be acquired.

Accordingly, if the telescopic shaft serves as the torquetransfer/slide/buffer mechanism, the buffer mechanism is providedseparately also on the yoke-side, the telescopic shaft having thethree-staged torsional rigidity characteristics can be provided.

For example, in the third embodiment, the male shaft is connected to theyoke of the Cardan shaft joint on the side of the steering wheel, andthe female shaft is connected to the yoke of the Cardan shaft joint onthe side of the steering gear. Conversely, the female shaft may beconnected to the yoke of the Cardan shaft joint on the side of thesteering wheel, and the male shaft may be connected to the yoke of theCardan shaft joint on the side of the steering gear.

As discussed above, according to the embodiment described above, whenthe torque is not transferred, two types of rolling members and slidemembers are employed, and the elastic body gives the pre-load to therolling members against the female shaft to the extent large enough notto cause the backlash, whereby the male shaft and the female shaft canslide in the axial direction with the stable slide load in a way thatsurely prevents the backlash between the male shaft and the femaleshaft.

When the torque is transferred, the slide members engage with the pairof axially-extending grooves in the peripheral direction and thus can berestricted, and further the rolling members can be restricted in theperipheral direction by the elastic body. The torque can be thereforetransferred in the high-rigidity state by certainly preventing thebacklash in the rotating direction between the male shaft and the femaleshaft.

Further, when the steering toque is equal to or smaller than thepredetermined level, the elastic body for the pre-load exhibits thelow-rigidity characteristic as the elastic body performs the pre-loadaction. While on the other hand, when the steering torque is equal to orlarger than the predetermined level, the slide members engage with thepair of axially-extending grooves in the peripheral direction andexhibit the high-rigidity characteristic.

Namely, when the steering torque is equal to or smaller than thepredetermined level, the elastic body buffers and reduces theuncomfortable noises and vibrations transferred from the engine room bythe pre-load action. While on the other hand, when the steering torquerises to become equal to or larger than the predetermined level, theslide members engage with the pair of axially-extending grooves, wherebythe steering torque can be transferred. Therefore, the feeling of sharpsteering can be acquired.

Accordingly, the torque transfer/slide mechanism serves also as thebuffer mechanism, and hence it is possible to provide the telescopicshaft exhibiting the two-staged torsional rigidity characteristics in away that effectively makes the use of the space and reduces both of thenumber of parts and manufacturing costs.

Moreover, according to the embodiment discussed above, when the steeringtorque is equal to or smaller than the predetermined level, the engagingmember does not engage with the engaged portion, and the buffer memberexhibits the low rigidity characteristic as it performs the bufferaction. When the steering torque is within the predeterminedintermediate range, the elastic body for the pre-load exhibits theintermediate rigidity characteristic as it performs the pre-load action.On the other hand, when the steering torque is equal to or larger thanthe predetermined level, the engaging member engages with the engagedportion, and the slide members engage with the pair of axially-extendinggrooves in the peripheral direction and exhibit the high rigiditycharacteristic.

Namely, when the steering torque is equal to or smaller than thepredetermined level, the engaging member does not engage with theengaged portion, and the buffer member can buffer and thus reduce theuncomfortable noises and vibrations transferred from the engine room.When the steering torque is within the predetermined intermediate range,the elastic body for the pre-load raises the torsional rigidity stepwiseas it performs the pre-load action. On the other hand, when the steeringtorque rises to become equal to or larger than the predetermined level,the engaging member engages with the engaged portion, and the slidemembers engage with the pair of axially-extending grooves in theperipheral direction, thus transferring the steering torque. The feelingof sharp steering can be therefore acquired.

Fourth Embodiment

FIG. 18A is a vertical sectional view of the telescopic shaft for thesteering of the vehicle according to a fourth embodiment of the presentinvention. FIG. 18B is a perspective view of a leaf spring as an elasticbody. FIG. 19 is a cross-sectional view taken along the line X-X in FIG.18A.

As illustrated in FIG. 18A, the telescopic shaft for the steering of thevehicle (which will hereinafter be termed the “telescopic shaft”) isconstructed of the male shaft 1 and the female shaft 2 that are fittedso as not to be rotatable but to be slidable on each other.

As shown in FIG. 19, three lines of grooves 3 extending in the axialdirection, are formed in an outer peripheral surface of the male shaft 1in a way that disposes these grooves equally at an interval (phase) of120 degrees in a peripheral direction thereof. Correspondingly in aninner peripheral surface of the female shaft 2, three lines of grooves 5extending in the axial direction, are formed in a way that disposesthese grooves equally at the interval (phase) of 120 degrees in theperipheral direction thereof.

A plurality of rigid spherical members 7 (rolling members, balls)rolling when the two shafts 1, 2 make relative movements in the axialdirection, are so interposed as to be rollable between theaxially-extending groove 3 of the male shaft 1 and the axially-extendinggroove 5 of the female shaft 2. Note that the axially-extending grooves5 of the female shaft 2 each takes substantially a circular-arc shape ora Gothic-arch shape in section.

The axially-extending groove 3 of the male shaft 1 is configured of apair of slant flat side surfaces 3 a and a bottom surface 3 b formedflat between the pair of flat side surfaces 3 a.

The leaf spring 9 making contact with the spherical member 7 and thusgiving pre-load thereto, is interposed between the axially-extendinggroove of the male shaft 1 and the spherical member 7.

The leaf spring 9 includes a spherical member sided contact portion 9 amaking contact at two points with the spherical member 7, a groovesurface sided contact portion 9 b spaced at a predetermined intervalsubstantially in the peripheral direction away from the spherical membersided contact portion 9 a and being in contact with the flat sidesurface 3 a of the axially-extending groove 3 of the male shaft 1, abiasing portion 9 c elastically biasing the spherical member sidedcontact portion 9 a and the groove surface sided contact portion 9 b insuch a direction as to get separated from each other, and a bottomportion 9 d facing to the bottom surface 3 b of the axially-extendinggroove 3.

The biasing portion 9 c is crooked a bent substantially in a U-shape andsubstantially in a circular-arc shape. The crooked biasing portion 9 cis capable of elastically biasing the spherical member sided contactportion 9 a and the groove surface sided contact portion 9 b so as toget separated from each other.

As shown in FIG. 19, three lines of grooves 4 extending in the axialdirection, are formed in the outer peripheral surface of the male shaft1 in a way that disposes these grooves equally at the interval (phase)of 120 degrees in the peripheral direction thereof. Correspondingly inthe inner peripheral surface of the female shaft 2, three lines ofgrooves 6 extending in the axial direction, are formed in a way thatdisposes these grooves equally at the interval (phase) of 120 degrees inthe peripheral direction thereof.

A plurality of rigid cylindrical members 8 (slide members, needlerollers) sliding when the two shafts 1, 2 make the relative movements inthe axial direction, are interposed with a minute gap between theaxially-extending groove 4 of the male shaft 1 and the axially-extendinggroove 6 of the female shaft 2. Note that the axially-extending grooves4, 6 are formed substantially in the circular-arc shape or theGothic-arch shape in section.

Further, as illustrated in FIG. 18A, a stopper plate 10 with an elasticbody is provided at the end portion of the male shaft 1, and serves toprevent the spherical members 7, the cylindrical members 8 and the leafsprings 9 from coming off.

Moreover, a lubricating agent is applied to between theaxially-extending groove 3 of the male shaft 1, the axially-extendinggroove 5 of the female shaft 2, the leaf spring 9 and the sphericalmember 7, thereby enabling the male shaft and the female shaft to slidein the axial direction with the stable slide load without any backlashwhen the torque is not transferred (during the slide).

In the thus constructed telescopic shaft, the spherical members 7 areinterposed between the male shaft 1 and the female shaft 2, and the leafsprings 9 give the pre-load to the spherical members 7 against thefemale shaft 2 to the extent large enough not to cause the backlash.When the torque is not transferred, it is therefore possible to surelyprevent the backlash between the male shaft 1 and the female shaft 2,and the male shaft 1 and the female shaft 2, when making the relativemovements in the axial direction, can slide with the stable slide loadwithout any backlash.

When torque is transferred, the leaf springs 9 elastically deform torestrict the spherical members 7 in the peripheral direction, and thethree lines of cylindrical members 8 interposed between the male shaft 1and the female shaft 2 perform the main function of transferring thetorque.

For example, when the torque is inputted from the male shaft 1, as thepre-load is applied from the leaf springs 9 at the initial stage, thereis no backlash, and the leaf springs 9 generate reactive force to thetorque, thus transferring the torque. At this time, the torque istransferred on the whole in a state of equilibrium between an inputtorque and a transfer torque among the male shaft 1, the leaf springs 9,the spherical members 7 and the female shaft 2.

As the torque further increases, there disappears a gap in the rotatingdirection between the male shaft 1 and the female shaft 2 through thecylindrical member 8, and an increment of the torque hereafter istransferred by the cylindrical members 8 through the male shaft 1 andthe female shaft 2. Hence, it is possible to surely prevent the backlashin the rotating direction between the male shaft 1 and the female shaft2 and also to transfer the torque in the high-rigidity state.

From what has been discussed so far, according to the fourth embodiment,the cylindrical members 8 in addition to the spherical members 7 areprovided, and hence a large proportion of the load quantity can besustained by the cylindrical members 8 when the large torque isinputted. Accordingly, the durability can be improved by restraining arise in contact pressure between the axially-extending groove 5 of thefemale shaft 2 and the spherical members 7, and the torque can betransferred in the high-rigidity state when the large torque load isapplied.

Furthermore, the cylindrical members 8 are in contact with the maleshaft 1 and the female shaft 2, so that the torsional torque to thespherical members 7 is reduced, and a lateral slip of the leaf spring 9is retrained, with the result that hysteresis can be restrained frombecoming excessive.

Thus, according to the fourth embodiment, the stable slide load isactualized, the backlash in the rotating direction is certainlyprevented, whereby the torque can be transferred in the high-rigiditystate.

Note that the spherical member 7, it is preferable, be a rigid ball.Further, it is preferable that the rigid cylindrical member 8 be aneedle roller.

The cylindrical member (which will hereinafter be referred to as theneedle roller) 8 receives the load in the line-to-line contact andtherefore exhibits a variety of effects such as being capable ofrestraining the contact pressure lower than by the ball receiving theload in the point-to-point contact, and so on. Accordingly, the needleroller 8 is more excellent in terms of the following items than in thecase of adopting the all-line ball rolling structure.

-   -   An attenuation effect at the slide portion is larger than by the        ball rolling structure. Hence, the vibration absorbing        performance is high.    -   The needle rollers make contact at their extremely small areas        with the male shaft and the female shaft, so that a slide load        fluctuation width can be restrained low. The vibrations caused        by the fluctuation thereof are not transferred up to the        steering.    -   If the same torque is transferred, the needle roller can        restrain the contact pressure low, and hence it is feasible to        decrease the length in the axial direction and to utilize the        space effectively.    -   If the same torque is transferred, the needle roller can        restrain the contact pressure low, and consequently there is no        necessity for an additional process for hardening the surface of        the axially-extending groove of the female shaft by a thermal        treatment, etc.    -   The number of parts can be decreased.    -   Assembly characteristics can be improved.    -   A cost for the assembly can be restrained.

Thus, the needle roller performs the key function of transferring thetorque between the male shaft 1 and the female shaft 2, and slidablycontacts with the inner peripheral surface of the female shaft 2. Theuse of the needle roller has the following superior points to theconventional spline fitting.

-   -   The needle rollers are mass-produced and are therefore extremely        low in their costs.    -   The needle roller, which is polished after the thermal        treatment, is therefore high of its surface hardness and        excellent of its abrasion resistance.    -   The needle roller is polished to gain fine surface roughness        thereof with the result that a frictional coefficient is low        when slid, and is therefore capable of restraining the slide        load low.    -   Lengths and layout of the needle rollers can be changed        according to the conditions for use, and hence the needle        rollers can correspond to a variety of applications without        changing the concept of design.    -   There might be a case where the frictional coefficient at the        sliding time must be further decreased depending on the        conditions for use, at which time the slide characteristic        thereof can be altered simply by effecting a surface treatment        on only the needle roller. The needle roller can therefore        correspond to the variety of applications without changing the        concept of design.    -   As the needle rollers with their outside diameters        differentiated on the order of every several microns can be        manufactured, gaps between the male shaft, the needle roller and        the female shaft can be minimized. Hence, an improvement in the        rigidity of the shaft in the torsional direction can be        facilitated.

Next, an examination will be made by comparing German Patent DE3730393C2with the present fourth embodiment.

FIG. 20 is an enlarged partial sectional view of the telescopic shaftfor the steering of the vehicle in the fourth embodiment of the presentinvention, showing a state when the torque is not transferred.

FIG. 21 is an enlarged partial sectional view of the telescopic shaftfor the steering of the vehicle in the fourth embodiment of the presentinvention, showing a state when the torque is transferred.

FIG. 37 is an enlarged partial sectional view of a telescopic shaft forsteering of a vehicle in German Patent DE3730393C2, showing a state whenthe torque is not transferred.

FIG. 38 is an enlarged partial sectional view of the telescopic shaftfor the steering of the vehicle in German Patent DE3730393C2, showing astate when the torque is transferred.

In German Patent DE3730393C2 shown in FIG. 37, when the torque is nottransferred (including a state where the torque is well balanced on theleft and right sides), for generating the pre-load between the maleshaft, the ball and the female shaft, the leaf spring is interposed in away that changes its curvature and a curvature of the axially-extendinggroove. In this state, however, a contact-point-to-contact-pointdistance (L1) between a contact point between the male shaft and theleaf spring and a contact point between the ball and the leaf spring, isextremely small. Besides, a gap (ΔS2: a quantity of flexure) is small,so that an excessive load occurs at the contact point between the leafspring and the ball, and a high stress occurs on the leaf spring.

In German Patent DE3730393C2 shown in FIG. 38, when the torque load isapplied, the contact-point-to-contact-point distance (L1) decreasesstepwise due to the flexure of the leaf spring. The distance L1 getsapproximate to zero as the torque increases, the load applied on thecontact point rises in proportion to the torque, and the stressgenerated on the leaf spring further increases. As this state repeatedlyoccurs, there might be a possibility in which a life-time of the torquetransfer unit can not be sustained long.

By contrast, according to the present fourth embodiment shown in FIGS.20 and 21, the leaf spring 9 can be sufficiently flexural at itsspherical member sided contact portion 9 a through the biasing portion 9c, and a sufficient quantity of flexure can be thus ensured.

Further, because of including the cylindrical members 8 in addition tothe spherical members 7, when the torque is transferred, the cylindricalmembers 8 make contact with the axially-extending grooves 4, 6 of themale shaft 1 and of the female shaft 2 earlier than the excessive load(stress) is applied on the leaf springs 9, and are capable of mainlytransferring the torque, and consequently the excessive load (stress) isapplied on neither the spherical members 7 nor the leaf springs 9.

Thus, the leaf spring 9 can ensure the sufficient quantity of flexure,and the excessive load (stress) is applied on neither the sphericalmembers 7 nor the leaf spring 9. Therefore, when the torque istransferred, the stress generated at the contact portion between thespherical member 7 and the leaf spring 9 can be relieved, whereby noneof the high stress occurs and the pre-load performance can be maintainedover a long period of time by preventing a “fatigue” due to thepermanent deformation.

Incidentally, in FIG. 20, when the torque is not transferred, the minutegaps exist between the cylindrical member 8 and the axially-extendinggroove 4 of the male shaft 1 and between the cylindrical member 8 andthe axially-extending groove 6 of the female shaft 2, however, thecylindrical members 8 abut onto the grooves.

In German Patent DE3730393C2 shown in FIGS. 37 and 38, a sectionalconfiguration of the axially-extending groove of the male shaft, inwhich the leaf spring is disposed, is a circular-arc shape having acurvature, and the leaf spring also assumes a circular-arc shape havinga curvature, wherein the leaf spring is given spring characteristic bychanging the respective curvatures.

Hence, the contact points between the leaf spring and the male shaftare, as shown in FIG. 37, corners of the male shaft. Accordingly, asillustrated in FIG. 38, when the torque load is applied, the whole ofthe leaf spring slides sideways, thereby inducing a decrease in thetransfer torque and causing the excessive hysteresis.

In contrast, in the present fourth embodiment illustrated in FIGS. 20and 21, the axially-extending groove 3 of the male shaft 1 is configuredof the flat surfaces. A central line of the axially-extending groove 3is directed to a central point of the male shaft 1, wherein the groove 3takes a wedge-like shape showing a symmetry between the right and lefthalves with respect to the center of the axially-extending groove 3. Anangle (contact angle) of the wedge is preferably 40 through 70 degreesto the center of the axially-extending groove 3. With this contrivance,the leaf spring 9 is firmly fixed to the wedge surfaces of theaxially-extending groove 3, and hence, when the torque load is applied,the whole of the leaf spring 9 is hard to slide sideways. Therefore, thetransfer torque does not decrease, and the occurrence of the excessivehysteresis can be prevented.

In German Patent DE3730393C2 shown in FIGS. 37 and 38, when the torqueload is not applied, none of the contact points between the male shaft,the spherical member, the leaf spring and the female shaft exist on thesame line, so that the contact angle comes to change according as thetorque load is applied. As a result, there might be a possibility inwhich neither a linear torsional characteristic necessary for thesteering shaft nor the proper hysteresis can be obtained.

By contrast, according to the present fourth embodiment shown in FIGS.20 and 21, the contact points between the male shaft 1, the sphericalmember 7, the leaf spring 9 and the female shaft 2 stay on the same lineirrespective of the state of the torque load, and therefore the contactangle does not change. This makes it possible to acquire the lineartorsional characteristic necessary for the steering shaft and also thelinear steering characteristic giving the feeling of the high rigidity.

FIGS. 22A, 22B and 22C are schematic views showing flexural states ofthe leaf springs employed in the respective embodiments of the presentinvention.

FIGS. 39A and 39B are schematic views showing flexural states of theleaf springs used in German Patent DE3730393C2.

FIGS. 39A and 39B show simplified models of the leaf spring shown inGerman Patent DE3730393C2. FIG. 39A shows a state where it is desiredthat a proper pre-load be applied in a non-load state of the torque,wherein a distance (C2) between the leaf spring and theaxially-extending groove serves as a stroke at which the pre-load can begenerated as a spring. FIG. 39B shows that when load (F1) is applied attwo points, the leaf spring becomes flexural and eventually contactswith the side surfaces of the axially-extending groove. Consequently,the leaf spring must receive all the torque at the points contactingwith the ball. Accordingly, the leaf spring is unable to increase aquantity of flexure (ΔS2) thereof, and it is presumed that the steeringshaft is hard to sustain its necessary life-time. Note that arelationship between the distance (C2) and the quantity of flexure (ΔS2)is given by C2≦ΔS2.

By contrast, according to the fourth embodiment of the present inventionillustrated in FIG. 22A, an interval between the spherical member sidedcontact portion 9 a and the groove surface sided contact portion 9 b ofthe leaf spring 9 is set to (C1). In this state, when the load (F1) isapplied at two points (corresponding to the spherical member sidedcontact portion 9 a), the elastic body can sufficiently get flexural,and an ample quantity of flexure (ΔS1) can be ensured. Accordingly, thepre-load performance can be maintained over the long period of time bypreventing the “fatigue” due to the permanent deformation. Note that arelationship between the interval (C1) and the quantity of flexure (ΔS1)is given by C1>ΔS1.

In an embodiment (which will hereinafter be described by way of a sixthembodiment) of the present invention shown in FIG. 22B, the intervalbetween the spherical member sided contact portion 9 a and the groovesurface sided contact portion 9 b of the leaf spring 9 is set to (C1).In this state, when the load (F1) is applied at two points(corresponding to the spherical member sided contact portion 9 a), theelastic body can sufficiently get flexural, and the ample quantity offlexure (ΔS1) can be ensured. Hence, the pre-load performance can bemaintained over the long period of time by preventing the “fatigue” dueto the permanent deformation. Note that a relationship between theinterval (C1) and the quantity of flexure (ΔS1) is given by C1>ΔS1.

In an embodiment (which will hereinafter be described by way of aseventeenth embodiment) of the present invention shown in FIG. 22C, theinterval between the spherical member sided contact portion 9 a and thegroove surface sided contact portion 9 b of the leaf spring 9 is set to(C1), and the biasing portion 9 c is formed of a rubber, a syntheticresin and so on. In this state; when the load (F1) is applied at twopoints (corresponding to the spherical member sided contact portion 9a), the elastic body can sufficiently get flexural, and the amplequantity of flexure (ΔS1) can be ensured. Accordingly, the pre-loadperformance can be maintained over the long period of time by preventingthe “fatigue” due to the permanent deformation. Note that therelationship between the interval (C1) and the quantity of flexure (ΔS1)is given by C1>ΔS1.

Next, as described above, when the torque is applied, the whole of theleaf spring 9 is so structured as to be hard to slide sideways, however,the bottom portion 9 d of the leaf spring 9 is allowed to slightly shiftsideways from the bottom surface 3 b of the axially-extending groove 3.

Namely, the bottom portion 9 d of the leaf spring 9, as in the presentfourth embodiment, is set in the contact-state with the bottom surface 3b of the axially-extending groove 3, or as in a fifth embodiment whichwill be explained later on, an interval from the bottom surface 3 b ofthe axially-extending groove 3 is set to a predetermined interval.

Hence, the bottom portion 9 d of the leaf spring 9 is made contact withthe bottom surface 3 b of the axially-extending groove 3 as thenecessity may arise, thereby making it possible to control thehysteresis and to obtain the hysteresis as desired.

Namely, it is required that the hysteresis be changed in many ways inmatching with the steering performance of each vehicle. To be specific,in a case where the bottom portion 9 d of the leaf spring 9 is set inthe contact-state with the bottom surface 3 b of the axially-extendinggroove 3, a friction occurs when the axially-extending groove 3 and theleaf spring 9 make the relative movements, and the hysteresis can be setcomparatively large. On the other hand, the interval between the bottomsurface 3 b of the axially-extending groove 3 and the bottom portion 9 dof the leaf spring 9 is set to the predetermined interval, in which casenone of the friction occurs when the axially-extending groove 3 and theleaf spring 9 make the relative movements, and the hysteresis can be setcomparatively small.

Fifth Embodiment

FIG. 23 is a cross-sectional view (corresponding to a cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a fifth embodiment of the presentinvention.

The fifth embodiment is substantially the same as the fourth embodimentdiscussed above, wherein the bottom surface 3 b of the axially-extendinggroove 3 and the bottom portion 9 d of the leaf spring 9 are spaced at apredetermined interval.

Accordingly, in this case, as explained above, the hysteresis can becontrolled and can be set comparatively small without the occurrence ofthe friction when the axially-extending groove 3 and the leaf spring 9move relatively.

Sixth Embodiment

FIG. 24 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a sixth embodiment of the presentinvention.

The sixth embodiment is substantially the same as the fifth embodimentdiscussed above, wherein the spherical member sided contact portion 9 aof the leaf spring 9 is formed at a folding side end portion of the leafspring 9, and the groove surface sided contact portion 9 b is formed ata folding intermediate portion of the leaf spring 9.

Further, as in the fifth embodiment discussed above, the bottom surface3 b of the axially-extending groove 3 and the bottom portion 9 d of theleaf spring 9 are spaced at a predetermined interval.

Seventh Embodiment

FIG. 25 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a seventh embodiment of the presentinvention.

The seventh embodiment is substantially the same as the fourthembodiment discussed above, wherein the spherical member sided contactportion 9 a of the leaf spring 9 is formed with a protruded portion 9 eprotruding towards the groove surface sided contact portion 9 b.

This configuration enables the spherical member sided contact portion 9a to make contact at four points with the spherical member 7 and theload at the contact points between the leaf spring 9 and the sphericalmember 7 to be decreased, whereby the stress can be relieved.

Moreover, the bottom portion 9 d of the leaf spring 9 is set in thecontact-state with the bottom surface 3 b of the axially-extendinggroove 3. In this case, as described above, the hysteresis can becontrolled, the friction occurs when the axially-extending groove 3 andthe leaf spring 9 move relatively, and the hysteresis can be setcomparatively large.

Eighth Embodiment

FIG. 26 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in an eighth embodiment of the presentinvention.

The eighth embodiment is substantially the same as the seventhembodiment discussed above, wherein the bottom surface 3 b of theaxially-extending groove 3 and the bottom portion 9 d of the leaf spring9 are spaced at a predetermined interval.

Accordingly, in this case, as explained above, the hysteresis can becontrolled and can be set comparatively small without the occurrence ofthe friction when the axially-extending groove 3 and the leaf spring 9move relatively.

Ninth Embodiment

FIG. 27 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a ninth embodiment of the presentinvention.

The ninth embodiment is substantially the same as the fourth embodimentdiscussed above, wherein tip end portions of the groove surface sidedcontact portion 9 b of the leaf spring 9 are folded inwards to makecontact with the spherical member sided contact portions 9 a thereof.

This contrivance enables an increase in the rigidity of the leaf spring9 and an improvement of the torsional rigidity.

Tenth Embodiment

FIG. 28 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a tenth embodiment of the presentinvention.

The tenth embodiment is substantially the same as the ninth embodimentdiscussed above, wherein the bottom surface 3 b of the axially-extendinggroove 3 and the bottom portion 9 d of the leaf spring 9 are spaced at apredetermined interval.

Accordingly, in this instance, as described above, the hysteresis can becontrolled and can be set comparatively small without the occurrence ofthe friction when the axially-extending groove 3 and the leaf spring 9move relatively.

Eleventh Embodiment

FIG. 29 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in an eleventh embodiment of the presentinvention.

The eleventh embodiment is substantially the same as the sixthembodiment discussed above, wherein the spherical member sided contactportion 9 a of the leaf spring 9 is formed on the folded-back endportion of the leaf spring 9, and the groove surface sided contactportion 9 b is formed at a folding intermediate portion of the leafspring 9. In this case also, the same action and effects as those in thethird embodiment discussed above can be exhibited.

A tip end portions of the spherical member sided contact portion 9 a ofthe leaf spring 9 are folded outwards to make contact with the groovesurface sided contact portions 9 b. With this contrivance, the rigidityof the leaf spring 9 can be increased, and the torsional rigidity can beimproved.

Twelfth Embodiment

FIG. 30 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a twelfth embodiment of the presentinvention.

The twelfth embodiment is substantially the same as the fourthembodiment discussed above, wherein the crooked biasing portion 9C ofthe leaf spring 9 is eliminated, a pair of spherical member sidedcontact portions 9 a are constructed of an inside plate 9 f bentsubstantially in a U-shape, and a pair of groove surface sided contactportions 9 b are constructed of an outside plate 9 g bent substantiallyin a U-shape. Biasing portions 9 h formed of different elastic materialssuch as rubbers or synthetic resins, etc. are interposed between flatsurfaces of the inside plate 9 f and flat surfaces of the outside plate9 g.

Further, there is no gap between a bottom surface of the inside plate 9f and a bottom surface of the outside plate 9 g, wherein these bottomsurfaces are set in a contact state. In this case, the hysteresis can becontrolled, the friction occurs when the inside plate 9 f and theoutside plate 9 g move relatively, and the hysteresis can be setcomparatively large.

Thirteenth Embodiment

FIG. 31 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a thirteenth embodiment of the presentinvention.

The thirteenth embodiment is substantially the same as the twelfthembodiment discussed above, wherein there is a slight gap between thebottom surface of the inside plate 9 f and the bottom surface of theoutside plate 9 g, wherein these bottom surfaces are set in anon-contact state. In this case, the hysteresis can be controlled, noneof the friction occurs when the inside plate 9 f and the outside plate 9g move relatively, and the hysteresis can be set comparatively small.

Fourteenth Embodiment

FIG. 32 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a fourteenth embodiment of the presentinvention.

The fourteenth embodiment is substantially the same as the fourthembodiment discussed above, wherein in the leaf spring 9, second biasingportions 9 j formed of different elastic materials such as rubbers or asynthetic resins, etc. are interposed between the spherical member sidedcontact portions 9 a and the grove surface sided contact portions 9 b.

With this configuration, the elasticity inherent in the differentelastic material is added to the elasticity inherent in the body of theleaf spring 9 itself, whereby the higher torsional rigidity can beacquired.

Fifteenth Embodiment

FIG. 33 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a fifteenth embodiment of the presentinvention.

The fifteenth embodiment is substantially the same as the fifthembodiment discussed above, wherein in the leaf spring 9, the secondbiasing portions 9 j formed of different elastic materials such asrubbers or a synthetic resins, etc. are interposed between the sphericalmember sided contact portions 9 a and the groove surface sided contactportions 9 b.

With this configuration, the elasticity inherent in the differentelastic material is added to the elasticity inherent in the body of theleaf spring 9 itself, whereby the higher torsional rigidity can beacquired.

Sixteenth Embodiment

FIG. 34 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a sixteenth embodiment of the presentinvention.

The sixteenth embodiment is substantially the same as the sixthembodiment discussed above, wherein in the leaf spring 9, the secondbiasing portions 9 j formed of different elastic materials such asrubbers or synthetic resins, etc. are interposed between the sphericalmember sided contact portions 9 a and the grove surface sided contactportions 9 b.

With this configuration, the elasticity inherent in the differentelastic material is added to the elasticity inherent in the body of theleaf spring 9 itself, whereby the higher torsional rigidity can beacquired.

Seventeenth Embodiment

FIG. 35 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in a seventeenth embodiment of the presentinvention.

The seventeenth embodiment is substantially the same as the twelfth orthirteenth embodiment discussed above, wherein in the leaf spring 9, apair of spherical member sided contact portions 9 a are constructed oftwo pieces of plates as inside plates, and a pair of groove surfacesided contact portions 9 b are constructed of an outside plate 9 g bentsubstantially in a U-shape. The biasing portions 9 h formed of differentelastic materials such as rubbers or a synthetic resins, etc. areinterposed therebetween.

With this configuration, the elasticity inherent in the material itselfcan be utilized, and, especially in the case of requiring the lowtorsional rigidity, the characteristic thereof can be exhibited.

Eighteenth Embodiment

FIG. 36 is a cross-sectional view (corresponding to the cross-sectionalview taken along the line X-X in FIG. 18A) of the telescopic shaft forthe steering of the vehicle in an eighteenth embodiment of the presentinvention.

The eighteenth embodiment is what the leaf spring 9 is provided on theside of the female shaft 2 in the fourth embodiment discussed above.

The axially-extending groove 5 of the female shaft 2 is constructed of apair of slant flat side surfaces 5 a and a bottom surface 5 b formedflat between the pair of flat side surfaces 5 a.

The leaf spring 9, which makes contact with the spherical member 7 andthus gives the pre-load thereto, is provided between theaxially-extending groove 5 of the female shaft 2 and the sphericalmembers 7.

The leaf spring 9 includes the spherical member sided contact portions 9a making contact at two points with the spherical member 7, the groovesurface sided contact portions 9 b spaced at a predetermined intervalsubstantially in the peripheral direction from the spherical membersided contact portions 9 a and making contact with the flat sidesurfaces 5 a of the axially-extending groove 5 of the female shaft 2,biasing portions 9 c for elastically biasing the spherical member sidedcontact portions 9 a and the groove surface sided contact portions 9 bin such a direction as to get separated from each other, and the bottomportion 9 d facing the bottom surface 5 b of the axially-extendinggroove 5.

The biasing portion 9 c is bent substantially in a circular-arc shapeand thus takes substantially a U-shape. The biasing portion 9 c takingthe bent shape can elastically bias the spherical member sided contactportion 9 a and the groove surface sided contact portion 9 b in such adirection as to get separated from each other.

Thus, even when the leaf spring 9 is disposed conversely to the fourthembodiment, the same action and effects can be exhibited.

Note that the present invention can be modified in a variety of formswithout being limited to the embodiments discussed above.

As explained so far, according to the fourth through eighteenthembodiments of the present invention, the elastic body includes thetransfer member sided contact portions making contact with the firsttorque transfer member, the groove surface sided contact portions spacedat the predetermined interval substantially in the peripheral directionfrom the transfer member sided contact portions and making contact withthe groove surfaces of the axially-extending groove of the male shaft orthe female shaft, and the biasing portions for elastically biasing thetransfer member sided contact portions and the groove surface sidedcontact portions in such a direction as to get separated from eachother. Therefore, in the elastic body, the transfer member sided contactportions can gain the sufficient flexures through the biasing portions,and the ample quantities of flexures can be ensured.

Further, as the second torque transfer member in addition to the firsttorque transfer member is provided, when the torque is transferred, thesecond transfer members make contact with the axially-extending groovesof the male shaft and of the female shaft earlier than the excessiveload (stress) is applied on the elastic body, and are capable of mainlytransferring the torque, and consequently the excessive load (stress) isapplied on neither the first torque transfer members nor the elasticbody.

Moreover, the elastic body can, as described above, ensure thesufficient quantity of flexure, and the excessive load (stress) isapplied on neither the first torque transfer members nor the elasticbody. Hence, when the torque is transferred, the stress generated at thecontact portion between the first torque transfer member and the elasticbody can be relieved. This prevents the high stress from occurring, andthe pre-load performance can be maintained over the long period of timeby preventing the “fatigue” due to the permanent deformation.

Still further, in the elastic body, the transfer member sided contactportions thereof make contact with the first torque transfer member, andthe groove surface sided contact portions thereof make contact with thegroove surface of the axially-extending groove. Therefore, the elasticbody is in the state of fitting to the axially-extending groove.Accordingly, when the torque is transferred, the whole of the elasticbody is hard to slide sideways in the peripheral direction from theaxially-extending groove. Hence, the decrease in the transfer torque isnot induced, and the hysteresis can be prevented from becomingexcessive.

Furthermore, the contact points between the male shaft, the sphericalmember, the elastic body and the female shaft stay on the same lineirrespective of the state of the torque load, and therefore the contactangle does not change. This makes it possible to acquire the lineartorsional characteristic necessary for the steering shaft and also thelinear steering characteristic giving the feeling of the high rigidity.

Note that manufacturing errors of the male shaft, the female shaft andthe elastic body can be absorbed by the elastic deformation of theelastic body, so that a tolerance can be set large and a scheme ofreducing the costs can be attained.

From what has been discussed so far, according to the fourth througheighteenth embodiments of the present invention, the stress generated onthe elastic body is relieved, whereby the pre-load performance requiredover the long period of time can be maintained by preventing the“fatigue” of the elastic body. Further, there is no necessity of settingthe dimensional accuracy strict, and the reduction in the costs can beactualized. Moreover, the steering performance required can be easilyobtained because of being structured so that the friction between theelastic body and the axially-extending groove can be controlled.

1. A telescopic shaft for steering of a vehicle, assembled in a steeringshaft and including a male shaft and a female shaft that are so fittedas to be capable of transferring torque and to be movable in an axialdirection relative to each other, characterized in that a rolling memberis fitted through an elastic body for pre-load between at least a pairof axially-extending grooves formed in an outer peripheral surface ofsaid male shaft and in an inner peripheral surface of said female shaft,a slide member is fitted in between at least another pair ofaxially-extending grooves formed in the outer peripheral surface of saidmale shaft and in the inner peripheral surface of said female shaft, andwhen a steering torque is equal to or smaller than a predeterminedlevel, said elastic body for the pre-load exhibits a low rigiditycharacteristic as said elastic body performs pre-load action; when thesteering torque is equal to or larger than the predetermined level, saidslide member exhibits a high rigidity characteristic as said slidemember engages with said pair of axially extending grooves; andtwo-staged torsional rigidity characteristics of the low rigiditycharacteristic and the high rigidity characteristic, are therebyprovided.
 2. A telescopic shaft for steering of a vehicle according toclaim 1, wherein said elastic body for the pre-load is constructed ofone piece of leaf spring.
 3. A telescopic shaft for steering of avehicle according to claim 1, wherein said elastic body for the pre-loadis constructed of a composite body formed of different materials.
 4. Atelescopic shaft for steering of a vehicle with a universal joint, to beassembled in a steering shaft, including a male shaft and a female shaftthat are so fitted as to be capable of transferring torque and to bemovable in an axial direction relative to each other, and receiving aconnection of a yoke of the universal joint, characterized in thatrolling members are fitted through an elastic body for pre-load betweenat least a pair of axially-extending grooves formed in an outerperipheral surface of said male shaft and in an inner peripheral surfaceof said female shaft, a slide member is fitted in between at leastanother pair of axially-extending grooves formed in the outer peripheralsurface of said male shaft and in the inner peripheral surface of saidfemale shaft, a buffer member is interposed between said yoke and anyone of said male shaft and said female shaft, said yoke is formed withan engaged portion, and any one of said male shaft and said female shaftis provided with an engaging member capable of engaging with anddisengaging from said engaged portion, and when a steering torque isequal to or smaller than a predetermined level, said engaging memberdoes not engage with said engaged portion while said buffer memberexhibits a low rigidity characteristic as said buffer member performsbuffer action; when the steering torque falls within a predeterminedintermediate range, said elastic body for the pre-load exhibits anintermediate rigidity characteristic as said elastic body performspre-load action; when the steering torque is equal to or larger than thepredetermined level, said engaging member engages with said engagedportion while said slide member exhibits a high rigidity characteristicas said slide member engages with said pair of axially-extending groovesin a peripheral direction; and three-staged torsional rigiditycharacteristics of the low rigidity characteristic, the intermediaterigidity characteristic and the high rigidity characteristic, arethereby provided.
 5. A telescopic shaft for steering of a vehicle,assembled in a steering shaft and including a male shaft and a femaleshaft that are so fitted as to be capable of transferring torque and tobe movable in an axial direction relative to each other, characterizedin that a first torque transfer portion, which includes a first torquetransfer member and an elastic body for pre-load, is formed between anouter peripheral surface of said male shaft and an inner peripheralsurface of said female shaft, a second torque transfer portion is formedbetween the outer peripheral surface of said male shaft and the innerperipheral surface of said female shaft, and when a steering torque isequal to or smaller than a predetermined level, said elastic body forthe pre-load exhibits a low rigidity characteristic as said elastic bodyperforms pre-load action; when the steering torque is equal to or largerthan the predetermined level, said second torque transfer portionexhibits a high rigidity characteristic; and two-staged torsionalrigidity characteristics of the low rigidity characteristic and the highrigidity characteristic, are thereby provided.